Generally, the bodies of electrical boxes include internal securing means for securing an accessory support, and include external fastener means for fastening to the wall. The accessory support makes it possible to mount any type of accessory mechanism in the inside volume of the body of the electrical box, merely by snap-fastening the accessory mechanism on the accessory support.
Furthermore, and usually, the bodies of known electrical boxes include, in their rear portion, knock-out diaphragms that make it possible to open the wall of the body locally so as to insert, into its inside volume, electrical conduit from which there emerge the electrical conductors necessary for serving the accessory mechanism fitted on the accessory support.
The bodies of the electrical boxes present sizes that are standard.
Thus, currently, the bodies of a circular electrical box for flush mounting present a standard diameter of 68 millimeters (mm) and usually a depth of 40 mm.
The inside volume of the body of such an electrical box is thus small and it is awkward to house therein not only the accessory mechanism mounted on the accessory support, but also the ends of the electrical conductors that have been pulled into the inside volume of the body of the electrical box in order to connect them to the accessory mechanism, in particular because of the stiffness of the electrical conductors that need to be bent between the accessory mechanism and the rear wall of the body of the box and because of the space that the end of the conduit may occupy.
In addition, the inside volume restricts any possible development of electrical accessories that are prevented from incorporating all of the functions that might be desired, because of their limited size.
The solution currently used for housing voluminous electrical accessories thus consists in providing two electrical boxes side by side, with one housing the electrical accessory, while the other houses the electrical conductors.
However, this solution turns out to be costly and tricky to implement.
In addition, Document U.S. Pat. No. 4,669,804 discloses an electrical box that is fitted with connection terminals having electric wires coming from the local electricity network.
More precisely, the electrical box comprises a body, three electrical-connection elements, and a rear block for fitting to the rear of the body.
The body presents a side wall that is closed at the rear by a rear wall so as to define an inside volume for receiving an accessory mechanism, and that is bordered at the front by a peripheral collar that is adapted to bear against the wall surface.
The three electrical-connection elements are situated at the rear of the rear wall of the body. Each of them is accessible via the inside volume of the body, through respective ones of three slots that are provided in the rear wall of the body, and each of them includes an outside terminal.
The rear block is designed to be fitted to the rear of the body, in such a manner as to block the three electric wires in the outside terminals of the three electrical-connection elements.
The rear block is arranged in such a manner that it is not necessary to cut the three electric wires. On the contrary, provision is made to connect the electrical box on the path of the three electric wires.
The major drawback of that electrical box is that it is difficult to connect the electric wires to the outside terminals.
Specifically, connection requires having access to the rear of the wall for positioning the electric wires in the rear block, then for fitting the rear block on the body. In practice, the installer rarely has access to the rear of the wall.
Another drawback of that electrical box is that, as described, connecting the electric wires requires fitting the rear block against the body, by a movement in translation. That is why the rear body is distinct from the body and is not movably mounted thereon. The number of distinct elements to be manipulated by the installer is thus large, which complicates the installer's work and increases the risk of losing one of the components of the electrical box.